Pumped refrigerant loop cooling system for cooling High thermal density heat loads

ABSTRACT

A cooling system for transferring heat from a heat load to an environment has a volatile working fluid. The cooling system includes first and second cooling cycles that are thermally connected to the first cooling cycle. The first cooling cycle is not a vapor compression cycle and includes a pump, an air-to-fluid heat exchanger, and a fluid-to-fluid heat exchanger. The second cooling cycle can include a chilled water system, or a vapor compression system, for transferring heat from the fluid-to-fluid heat exchanger to the environment. The pump circulates the vaporizable refrigerant to the evaporator device associated with the air stream within the rack or enclosure. The heated air causes the refrigerant to evaporate within the evaporator device. This evaporated refrigerant travels to a condenser device cooled by another thermally cooler fluid, causing the refrigerant to condense back to a liquid, return to the pump, and begin the cycle again.

TECHNICAL FIELD

The present invention relates to the cooling of electrical and electronic components, and more particularly, to use of a pumped refrigerant loop to cool high thermal density computer and telecommunications racks and enclosures.

BACKGROUND OF THE INVENTION

Advancements in information technology (IT) equipment present challenges in creating a more effective IT environment in data centers and networking facilities. Equipment enclosures designed for high power density applications employing servers and networking equipment typically must provide not only effective cable management and power distribution, but also adequate cooling and ventilation to assure proper and reliable operation of equipment. Insufficient cooling air can cause overtemperature shutdown and unreliable performance and reduced lifetime of the equipment.

Computer and telecommunication racks and enclosures have become increasingly thermally dense. The number of electronic heat generating sources within these racks and enclosures continues to increase as does the quantity of heat that needs to be dissipated. Current practice to cool computer and telecommunication racks and enclosures in raised floor data centers uses cooled air, forced through perforated tiles in the floor, whereby that air enters the enclosure or rack to be cooled and that air moves past extended surface heat sinks mounted on the devices to be cooled. The heat sinks then dissipate that heat to the moving air stream and finally the heated air leaves the rack or enclosure to circulate back to another location where it can be cooled again and recirculated. This air stream can be circulated in the enclosure from front to back or from bottom to top depending on the configuration of the devices and architecture of the systems which need cooling. Additionally, fans may be used within the enclosures or racks to assist with air movement across the heat sink dissipation surfaces.

As computers and telecommunication devices become more powerful they must as a necessity give off more heat. This is a direct consequence of what has become known as Moore's Law. Moore's law is the empirical observation that the complexity of integrated circuits, with respect to minimum component cost, doubles every 24 months. The current method of increasing the cooling of these racks and enclosures has been to simply increase the airflow to and through the enclosures and racks. This means that a greater number of more powerful fans and blowers need to be added to the enclosures and racks to remove heat. Airflow has increased to the point where air velocity and acoustic noise are nearing unacceptable levels. Such substantial air movement in and around racks and enclosures causes cool air to mix with heated air, thus reducing the ability of the air stream to provide cooling.

Another disadvantage of the current method is the power consumption of the fans and blowers. As fans and blowers increase in capacity, the motors that drive them consume more power. This, in turn, causes more heat in the enclosure and surrounding room, thus exacerbating the problem. Dispersing all of the excess heat from the equipment and the surrounding room becomes even more of a challenge.

Yet another disadvantage of the current method of cooling enclosures occurs when air flows through the enclosure from bottom to top. As the air heats up as it removes heat from the components within the enclosure, the air temperature can be so hot as to damage the sensitive electronic components located at or near the top of the rack or enclosure.

Still another disadvantage occurs when the cooling air moves from the front to the rear of the rack or enclosure. Even if components do not overheat in the rear of the enclosure, the air exiting the enclosure at high velocities mixes with cooler room air before that cool air has had a chance to provide cooling to other enclosures. This, in turn, makes it more difficult to cool this mixed air stream with the computer room air conditioner since it requires a colder evaporator than might be required if the air stream did not mix.

It is seen then that there exists a continuing need for an improved method of removing heat from components when existing methods or systems are not feasible.

SUMMARY OF THE INVENTION

This need is met by the present invention wherein a pump is used to circulate a vaporizable (volatile) refrigerant, as a liquid, to an evaporator device located in close proximity to or in direct contact with the air stream within a computer or telecommunication rack or enclosure.

In accordance with one aspect of the present invention, a cooling system transfers heat from a heat load to an environment. The cooling system includes first and second cooling cycles that are thermally connected to the first cooling cycle. The first cooling cycle is not a vapor compression cycle and includes a pump, an air-to-fluid heat exchanger, and a fluid-to-fluid heat exchanger. The second cooling cycle can include a chilled water system, or a vapor compression system, for transferring heat from the fluid-to-fluid heat exchanger to the environment. The heated air within or near the enclosure causes a refrigerant to evaporate within an evaporator device. This evaporated refrigerant then travels through a tube or hose to a condenser device which can be located at some distance from the rack or enclosure. The condenser device is cooled by another thermally cooler fluid (air or liquid) which causes the refrigerant to condense back to a liquid. The liquid refrigerant then returns to the pump again through a tube or hose where it can begin the cycle again.

Accordingly, it is an object of the present invention to provide cooling to electrical and electronic components. It is a further object of the present invention to provide such cooling using a pumped refrigerant loop to cool high thermal density computer and telecommunication racks and enclosures.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of one embodiment of the pumped refrigerant loop system according to certain teachings of the rack intercooler in accordance with the present invention.

While the disclosed rack intercooler system is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawing and are described herein in detail. The figure and written description are not intended to limit the scope of the inventive concepts in any manner. Rather, the figure and written description are provided to illustrate the inventive concepts to a person of ordinary skill in the art by reference to particular embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the Figure, the disclosed cooling system, illustrated as a pumped refrigerant loop system 10, includes a refrigerant pump 12 which pumps a vaporizable refrigerant 14. The vaporizable refrigerant may be any fluid which changes from a liquid to a vapor with the addition of heat and has other thermophysical properties suitable for the application. One such refrigerant is R-134a, well known to those skilled in the art. There are many other refrigerants suitable for this application which those skilled in the art could suggest as well.

Continuing with FIG. 1, the present invention uses the pump 12 to circulate the vaporizable, or volatile, refrigerant 14, as a liquid, to an evaporator device 16 located in close proximity to or in direct contact with the air stream within a computer or telecommunication rack or enclosure 18. Conduits 20 serve to transport refrigerant to the evaporator device 16, a condenser 22, a liquid receiver 24, and back to the pump 12.

The rack enclosure 18, has an air inlet 26, located at the bottom of the enclosure 18, and an air discharge 28, located at the top of the enclosure 18. The airflow is induced by a fan 30. Devices 1,2,3,4,5,6,7 and 8 represent heat generating devices such as would be found in computers and telecommunication equipment. The heated air within or near the enclosure 18 causes the refrigerant 14 to evaporate within the evaporator device 16. As can be seen in FIG. 1, the evaporator coil 16 is located between heat generating devices 4 and 5. In this arrangement the heated air from devices 1,2,3 and 4 is cooled by evaporator 16 before the air reaches heat generating devices 5,6,7 and 8.

Continuing with FIG. 1, the evaporated refrigerant then travels through the conduits 20, such as tube or hose paths, to the condenser device 22. The condenser 22 can be located at some distance from the rack or enclosure 18, as suits the particular application and space constraints. Thus, the heat removed by the evaporator 16 is not able to reach devices 5,6,7 and 8, keeping them at acceptable temperature levels, while at the same time moving heat to the condenser 22, for dissipation remote from the rack enclosure 18.

The refrigerant pump 12 circulates refrigerant 14, in sufficient quantity to the evaporator 16 so that the air moving within enclosure 18 causes the refrigerant to vaporize and carry away heat generated by devices 1,2,3 and 4. The vaporized refrigerant 14, then travels through conduit 20 to the condenser 22. Condenser 22 in this embodiment is air cooled, whereby a cooling air flow 32 flows across the condenser by means of fan 34. However, the condenser 22 can be cooled by any thermally cooler fluid, including liquid or air, which causes the refrigerant to condense back to a liquid. This air flow 32 causes the refrigerant to condense back to the liquid state and return to the liquid receiver 24 by means of conduit 20. The liquid receiver 24, in turn, is connected to and returned to the pump 12, by conduit 20. Thus, the cycle is complete and starts again at the pump.

There are a number of advantages to using this invention over the prior art. By locating the evaporator device 16 close to or within the heated air stream of the rack or enclosure 18, a high evaporation temperature can be maintained and more heat can be removed for a given amount of airflow, thus reducing the total air flow required within the enclosure 18. Since the refrigerant 14 circulated by the pump 12 evaporates in the evaporator device 16, a large quantity of heat can be removed for a relatively small mass flow rate of refrigerant. Thus, the pump power required is small with respect to the fan or blower power, to do an equivalent amount of cooling by means of air alone. Heat is transported by refrigerant vapor by any suitable means, such as in a rigid tube or flexible hose, and therefore can be moved great distances for little expenditure of energy. This is unlike heated air which requires large ducts and open areas with many fans and blowers to move it any distance at all.

The condenser device 22 can be cooled by another fluid at a location remote from the evaporator 16. Thus, this invention can take advantage of cooler air within the room where the enclosures and racks are located without disturbing critical air flow patterns around dense racks. It is even possible with this method to locate the condenser device 22 in the outdoor ambient where free cooling is available when outdoor temperatures are below the air temperatures within the racks and enclosures. Further, the condenser device can use a fluid from a building air conditioning system to provide a means to condense the refrigerant. This may be building chilled water from a chilled water plant or cooling tower water from a building cooling tower. Use of either of these two fluid streams will make the condenser device particularly compact and efficient.

Having described the invention in detail and by reference to the preferred embodiment thereof, it will be apparent that other modifications and variations are possible without departing from the scope of the invention defined in the appended claims. 

1. A pumped refrigerant loop for transferring heat from a heat load to a heat exchange system, the pumped refrigerant loop comprising: a vaporizable refrigerant; a pump; a first heat exchanger in fluid communication with the pump and in thermal communication with the heat load; and a second heat exchanger having a first fluid path in fluid communication with the first heat exchanger and the pump, and a second fluid path connected to the heat exchange system, the first and second fluid paths being in thermal communication with one another.
 2. A pumped refrigerant loop as claimed in claim 1, wherein the first heat exchanger comprises an air to fluid heat exchanger.
 3. A pumped refrigerant loop as claimed in claim 1 wherein the first heat exchanger is in direct thermal contact with a heat source.
 4. A pumped refrigerant loop as claimed in claim 1 wherein the second heat exchanger comprises a fluid to fluid heat exchanger.
 5. A cooling system for transferring heat from a heat load to a heat exchange system, the cooling system comprising: a volatile working fluid; a pump; a first heat exchanger in fluid communication with the pump and in thermal communication with the heat load; and a second heat exchanger having a first fluid path in fluid communication with the first heat exchanger and the pump, and a second fluid path connected to the heat exchange system, the first and second fluid paths being in thermal communication with one another.
 6. The cooling system of claim 5, wherein the first heat exchanger comprises an air-to-fluid heat exchanger.
 7. The cooling system of claim 5, wherein the first heat exchanger is in direct thermal contact with a heat source.
 8. The cooling system of claim 5, wherein the second heat exchanger comprises a fluid-to-fluid heat exchanger.
 9. A cooling system for transferring heat from a heat load to an environment, the cooling system a first cooling cycle comprising a volatile working fluid and a second cooling cycle thermally connected to the first cooling cycle, wherein the first cooling cycle comprises a pump, a first heat exchanger in fluid communication with the pump and in thermal communication with the heat load, and a second heat exchanger having a first path for the working fluid connecting the first heat exchanger to the pump and a second path connected to the second cooling cycle, said first and second fluid paths being in thermal communication with one another; and wherein the second cooling cycle comprises a refrigeration system in thermal communication with the environment.
 10. The cooling system of claim 9, wherein the refrigeration system comprises: a compressor connected to one end of the second fluid path; a condenser in thermal communication with the environment, the condenser having an inlet connected to the compressor and an outlet connected to another end of the second path; and an expansion device positioned between the outlet of the condenser and the other end of the second path.
 11. A cooling system for transferring heat from a heat load to an environment, the cooling system comprising: a first cooling cycle containing a volatile working fluid; and a second cooling cycle thermally connected to the first cooling cycle; wherein the first cooling cycle comprises: a pump; a first heat exchanger in fluid communication with the pump and in thermal communication with the heat load; and a second heat exchanger having a first fluid path for the working fluid in fluid communication with the first heat exchanger and the pump, and a second fluid path comprising a portion of the second cooling cycle, wherein the first and second fluid paths are in thermal communication with one another, and wherein the second cooling cycle comprises a chilled water system in thermal communication with the environment.
 12. A cooling system for transferring heat from a heat load to an environment, the cooling system comprising: a pump for pumping a volatile working fluid through the system; a first heat exchanger connected to the pump and having a fluid path in thermal communication with the heat load; and a second heat exchanger having first and second fluid paths in thermal communication with one another, wherein the first fluid path provides fluid communication from the first heat exchanger to the pump, and wherein the second fluid path is adapted to connect the first heat exchanger to another cooling system that is in thermal communication with the environment. 